Known interactions

No interactions found.

What we now about Hedeoma pulegioides

Scientific Name: American pennyroyal

Other Names: European Pennyroyal, Hedeoma pulegioides, Lurk-In-The-Ditch, Mock Pennyroyal, Mosquito Plant, Penny Royal, Pudding Grass, Pulegium, Run-By-The-Ground, Squaw Balm, Squaw Mint, Stinking Balm, Thickweed, Tickweed

Who is this for?

Supplements are defined by the FDA as any products intended for ingestion as a supplement to the diet. If a product is sold as a supplement, it must state on its label "dietary supplement."

Unlike drugs, the statements on the manufacturer's label describing the role of dietary supplements need not be authorized by the FDA.4 To inform the consumer of this fact, the following statement is required by law to appear on the supplement label: "This statement has not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease."


American pennyroyal supplements are derived from the leaves and flowering tops of the plant known as: Hedeoma pulegeoides.5 The leaves and flowering tops are the source of pennyroyal oil which is mostly responsible for the medicinal properties of this herb.2 American pennyroyal grows in the eastern and northern United States and Canada. 5 Mentha pulegium is also referred to as American pennyroyal.

American pennyroyal is promoted for digestive disorders; pneumonia; inducing menstruation or abortions; and externally as an antiseptic, insect repellent, and for skin diseases. American pennyroyal is often promoted for use as an abortifacient (used to abort a fetus). It is true that a component of American pennyroyal oil may irritate the uterus causing uterine contraction, but this effect is unpredictable and so dangerous that it has been deadly.1,12,13

In animals, it is promoted for external use as a flea dip.

When should I be careful taking it?

The U.S. Food and Drug Administration (FDA) has stringent rules pertaining to safety, efficacy, and quality that pharmaceutical manufacturers must follow in order to market drugs in the U.S.6,7 Manufacturers of supplements do not have to follow these same rules to sell their products.8 For this reason, there is limited research evaluating supplements' safety and efficacy in the human body.9 As a result, those who choose to take these substances do so at their own risk.


Use of American pennyroyal by humans or animals is inadvisable due to its potentially harmful effects on the central nervous system, the liver and the kidneys.1,2

If American pennyroyal is substituted for proven remedies, it could allow the disease to advance beyond the point where proven therapies could help.

  • Digestive disorders can be serious conditions
  • Pneumonia is a potentially dangerous disease that requires treatment by a health care professional. It is a leading cause of death and disability in the United States. People at high risk (e.g. elderly, very young, or anyone with chronic obstructive pulmonary disease (COPD), diabetes mellitus, congestive heart failure, sickle cell anemia, AIDS, asthma, or one who is undergoing cancer therapy or organ transplantation) for developing pneumonia should contact their health care provider to discuss the possibility of vaccination.
  • Amenorrhea, the absence of cyclical menstruation could signify an abnormality in hypothalamic/pituitary and/or ovarian function. Potential consequences of untreated amenorrhea could include infertility, osteoporosis, cardiovascular disease, and if the disorder arises early in life, failure to go through puberty. Consultation with a health care professional is the best way to identify the most appropriate options for managing or treating any condition. Before using any dietary supplement, it is best to consult with your physician or pharmacist.

What side effects should I watch for?

Drugs must conform to certain regulatory proceedings, like manufacturer reporting, quality assurance, drug labeling, premarket clearance, benefit-risk assessment, and post-market monitoring, which facilitate the identification of serious adverse effects. Supplements generally do not have to conform to these processes, and therefore information on their adverse effects is limited.10

Pennyroyal oil derived from Mentha pulegium or the Hedeoma species is toxic to the central nervous system, liver, kidneys, and blood.11Potential adverse effects associated with the use of American pennyroyal include abdominal pain, nausea, vomiting, lethargy, dizziness, bleeding, increased blood pressure, increased pulse rate, agitation, lung problems, and dermatitis. In large portions, American pennyroyal can cause abortion, irreversible kidney damage, severe liver damage and death. A small amount of oil can produce delirium, unconsciousness, confusion, shock, seizures, and hearing or visual hallucination.1,13,14

American pennyroyal oil is also toxic to animals.

Adverse events reported to the FDA on a particular supplement can be viewed at http://www.cfsan.fda. gov/~dms/aems.html.

What interactions should I watch for?

People taking the following drugs may experience more side effects from pennyroyal: amiodarone (Cordarone), erythromycin (E-Base, E-Mycin, E.E.S., Ery-Tab, EryPed, Erythrocin, Ilosone, PCE Dispertab), clarithromycin (Biaxin), azithromycin (Zithromax), dirithromycin (Dynabac), troleandomycin (Tao), ketoconazole (Nizoral), miconazole (Monistat), itraconazole (Sporanox), fluconazole (Diflucan), omeprazole (Prilosec), Lansoprazole (Prevacid), pantoprazole (Protonix).17

Should I take it?

Although pennyroyal has many therapeutic claims, there are no clinical data to support the use of this herb. Together with the herb?s toxicity, the medicinal use of pennyroyal cannot be recommended.1,2

Dosage and Administration

Prescription and over-the-counter products are regulated by the FDA and therefore offer an advantage over supplements. Unlike the pharmaceutical companies, supplement manufacturers are not regulated, so the potencies and purity of supplements often differ by brand and even by bottle.15,16 The United States Pharmacopeia (USP), an agency that sets the standards of quality, purity, and consistency of products, is in the process of establishing standards for the manufacturing of some supplements, but the standards are optional and not all manufacturers follow them. To determine if the supplement manufacturer claims to follow USP standards, look for USPNF or USP on the supplement's label.

Carefully examine all the potential benefits and risks when considering the use of supplements.


Use of American pennyroyal by humans or animals is inadvisable due to its potentially harmful effects on the central nervous system, the liver and the kidneys. 1,2


  1. Anon: American pennyroyal, In Olin BR, ed.: The Review of Natural Products. St. Louis, MO, Facts and Comparisons< Jul 1998.
  2. Overview of dietary supplements. U.S. Food and Drug Administration Center for Food Safety and Applied Nutrition. Accessed 1999 June.
  3. Farley D. Benefit vs. risk: How the FDA approves new drugs. FDA Consumer Special Issue: From Test Tube to Patient: New Drug Development in the United States. 2nd ed U.S. Food and Drug Administration Accessed 1999 April.
  4. Flieger K. Testing drugs in people. FDA Consumer Special Issue: From Test Tube to Patient: New Drug Development in the United States. 2nd ed U.S. Food and Drug Administration Accessed 1999 April.
  5. Kurtzweil P, An FDA guide to dietary supplements. U.S. Food and Drug Administration Accessed 1999 Feb.
  6. Winslow LC, Kroll DJ. Herbs as medicines. Arch Intern Med.1998;158(9):2192-99.
  7. Statement by Joseph A. Levitt, Director, Center for Food Safety and Applied Nutrition, Food and Drug Administration, Department of Health and Human Services before the Committee on Government Reform U.S. House of Representatives May 27, 1999. Accessed 1999 June.
  8. POISINDEX< System: POISINDEX< Editorial Staff: Pennyroyal oil (Management/Treatment Protocol). In: Rumack BH, Hess AJ & Gelman CR (Eds): POISINDEX< System. MICROMEDEX, Englewood, Colorado (Edition expires [9/99]).
  9. Brinker F, ed. Herb Contraindications and Drug Interactions, 2nd ed. Sandy, Oregon: Eclectic Medical Publications;1998:110, 151, 179.
  10. Ernst E. De Smet. Risks associated with complementary therapies. In Dukes MNG, ed. Meyler's Side Effects of Drugs: an Encyclopedia of Adverse Reactions and Interactions. 13th ed. Amsterdam, Netherlands: Elsevier; 1996:1438.
  11. Ernst E. Treatments used in complementary medicine. In Aronson J K, ed. Side Effects of Drugs: an Encyclopedia of Adverse Reactions and Interactions. Amsterdam, Netherlands: Elsevier; 1998:491.
  12. Borins M. The dangers of using herbs: what your patients need to know. Postgrad Med.1998;104(1):91-100.
  13. Herbal Rx: the promises and pitfalls. Consumer Reports. March,1999.44-8.
  14. Fetrow CW, Avila JR. Professional?s Handbook of Complementary & Alternative Medicines. Springhouse Corporation; 1999.

(Note: The above information is not intended to replace the advice of your physician, pharmacist, or other healthcare professional. It is not meant to indicate that the use of the product is safe, appropriate, or effective for you.)

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